Lecture Notes: The Integumentary System

Overview

• Introduction to the integumentary system, the first organ system covered in Anatomy and Physiology 1.
• Focus on layers of the integument, characteristics, tissue types, and cells associated.
• Discussion on functions as barriers and appendages like sweat and oil (sebaceous) glands, erector pili muscle, and sensors.

Layers of the Integument

1. Epidermis

• Superficial Layer:
  • Consists of five sub-layers: stratum corneum, lucidum, granulosum, spinosum, and basal.
  • Composed of epithelial tissue; avascular.
• Key Cells:
  • Keratinocytes: provide strength, packed with keratin.
  • Melanocytes: produce melanin, give skin color, UV protection.
  • Dendritic Cells: immune surveillance.
  • Tactile Cells: sensory function.

2. Dermis

• Two Sub-layers:
  • Papillary Layer: loose areolar connective tissue; contains dermal papillae with capillaries and sense receptors (e.g., Meissner's corpuscles).
  • Reticular Layer: dense irregular connective tissue, provides strength and elasticity.
• Components: blood vessels, nerve endings, lymphatic vessels.

3. Hypodermis

• Not part of the skin; supports integument.
• Composed mainly of adipose tissue, provides insulation and shock absorption.

Functions of Integument

Protection

• Chemical Barrier:
  • Acidic secretions (acid mantle), antimicrobial peptides.
  • Melanin provides UV protection.
• Physical Barrier:
  • Keratinized cells form a protective barrier.
  • Prevents water loss and pathogen entry.
• Biological Barrier:
  • Immune cells (dendritic cells and macrophages) surveil and respond to pathogens.

Thermoregulation

• Sweat Glands:
  • Eccrine: widespread, thermoregulation.
  • Apocrine: found in specific areas, unclear function.
• Vascular adjustments:
  • Vasodilation and vasoconstriction regulate heat loss and retention.

Other Functions

• Cutaneous sensations (temperature, touch, and pain).
• Metabolic functions, including vitamin D synthesis.
• Blood reservoir: manages up to 5% of body’s blood volume.
• Excretion of wastes through sweat.

Appendages of the Skin

Hair

• Developed from follicles, comprised of hard keratin.
• Contributes to sensory function and protection.
• Hair color determined by melanin.

Glands

• Sweat (Sodiferous) Glands:
  • Eccrine: open directly via pores for cooling.
  • Apocrine: open into hair follicles, function unclear.
• Sebaceous (Oil) Glands:
  • Associated with hair follicles, secrete sebum.
  • Lubricates and protects hair and skin.

Skin Pigments

• Melanin: primary determinant of skin color.
• Carotene: yellow-orange pigment, converted to vitamin A.
• Hemoglobin: contributes to color in lighter skin tones.

Diagnostic Indicators

• Cyanosis: blue tint indicating low oxygen.
• Erythema: redness associated with inflammation or fever.
• Pallor: paleness due to low blood flow.
• Jaundice: yellow skin due to liver dysfunction.

Homeostatic Imbalances

Skin Cancer

• Basal Cell Carcinoma: least malignant, originates in stratum basal.
• Squamous Cell Carcinoma: arises from keratinocytes of stratum spinosum.
• Melanoma: most dangerous, originates in melanocytes, follows ABCD rule for detection.

Burns

• First-degree: affects epidermis; redness and pain.
• Second-degree: affects epidermis and upper dermis; blistering.
• Third-degree: full thickness burn; needs skin grafting.

Conclusion

• Understanding of integumentary system's structure, function, and associated disorders is vital for further topics such as the skeletal system.
• Continuous review and integration of lecture and lab materials recommended.